Curved display device

This application claims priority to Korean Patent Application No. 10-2014-0037611, filed on Mar. 31, 2014 and Korean Patent Application No. 10-2015-0036079, filed on Mar. 16, 2015, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in their entireties are herein incorporated by reference.

1. Field

The disclosure herein relates to a curved display device, and more particularly, to a curved display device having a curved display area.

2. Description of the Related Art

Display devices are applied to various devices such as televisions, monitors, notebooks, mobile phones, and the like to display an image. In recent years, a curved display device is applied to the display devices. The curved display device is curved in a predetermined direction to provide a curved display area. The curved display device may provide the display area having the curved shape to provide an image having improved three-dimensional effect, immersion, and presence to a user.

The disclosure provides a curved display device having improved display quality.

Exemplary embodiments of the invention provide a curved display device including: a display substrate curved in a first direction on a plane, an opposite substrate coupled to the display substrate and curved together with the display substrate, and a liquid crystal layer including liquid crystal molecules disposed between the display substrate and the opposite substrate. In such an embodiment, the opposite substrate includes: a common electrode; and a first alignment layer disposed on the common electrode, where the first alignment layer aligns a first portion of the liquid crystal molecules at a first pretilt angle. In such an embodiment, the display substrate includes: a pixel electrode disposed on each of a plurality of pixel areas, where a plurality of slits is defined in the pixel electrode; and a second alignment layer disposed on the pixel electrode, where the second alignment layer aligns a second portion of the liquid crystal molecules at a second pretilt-angle, which is less than the first pretilt-angle.

In another exemplary embodiment, a curved display device includes a display substrate which is curved; an opposite substrate which is curved and disposed opposite to the display substrate; and a liquid crystal layer disposed between the display substrate and the opposite substrate, where the liquid crystal layer includes liquid crystal molecules. In such an embodiment, the opposite substrate includes: a first base substrate; and a first alignment layer disposed between the first base substrate and the liquid crystal layer, and the display substrate includes: a second base substrate; and a second alignment layer disposed between the second base substrate and the liquid crystal layer, where the second alignment layer includes reactive mesogens polymerized with each other. In such an embodiment, first liquid crystal molecules of the liquid crystal molecules, which are adjacent to the first alignment layer, have a first pretilt-angle, and the second liquid crystal molecules of the liquid crystal molecules, which are adjacent to the second alignment layer, have a second pretilt-angle different from the first pretilt-angle.

In another exemplary embodiment, a curved display device includes: a first base substrate which is curved; a first alignment layer including a first base layer disposed on the first base substrate and a plurality of first protrusions disposed on the first base layer; a second base substrate which is curved and disposed opposite to the first base substrate; and a second alignment layer including a second base layer disposed on the second base substrate and a plurality of second protrusions disposed on the second base layer. In such an embodiment, the first protrusions includes first large-size protrusions, each of which has a particle diameter of about 30 nanometers (nm) to about 1,000 nm, and the second protrusions include second large-size protrusions, each of which has a particle diameter of about 30 nm to about 1,000 nm. In such an embodiment, the first base layer includes: a first overlapping area which overlaps the first large-size protrusions; and a first non-overlapping area which does not overlap the first large-size protrusions, and the second base layer includes: a second overlapping area which overlaps the second large-size protrusions; and a second non-overlapping area which does not overlap the second large-size protrusions. In such an embodiment, a ratio of a surface area of first overlapping area to a surface area of second overlapping area is greater than zero (0) and equal to or less than ⅘.

The above and other feature of the invention will become apparent by describing in further detail exemplary embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1A is a perspective view of an exemplary embodiment of a curved display device according to the invention;

FIG. 1B is a plan view of the curved display device illustrated in FIG. 1A ;

FIG. 1C is a schematic cross-sectional view of an exemplary embodiment of the curved display device according to the invention;

FIG. 2 is a plan view of an exemplary embodiment of a pixel of the curved display device illustrated in FIG. 1A ;

FIG. 3A is a view of domains defined on the pixel illustrated in FIG. 2 ;

FIG. 3B is a cross-sectional view taken along line I-I′ of FIG. 2 ;

FIG. 4A is a cross-sectional view taken along line II-II′ of FIG. 2 .

FIG. 4B is an enlarged view of a first pretilt liquid crystal illustrated in FIG. 4A ;

FIG. 4C is a view of a second pretilt liquid crystal illustrated in FIG. 4A ;

FIGS. 5A to 5D are photographs illustrating brightness of first to eight domains according to the first and second pretilt-angles;

FIG. 6A is a schematic perspective view of an exemplary embodiment of the curved display device according to the invention;

FIG. 6B is a schematic perspective view of the pixel and the first and second alignment layers corresponding to the pixel in an exemplary embodiment of the curved display device according to the invention;

FIG. 6C is a schematic plan view of the first alignment layer shown in FIG. 6B ;

FIG. 6D is a schematic plan view of the second alignment layer shown in FIG. 6B ;

FIG. 6E is a schematic plan view of an overlapping area between the first and second alignment layers, a lower polarization plate, and an upper polarization plate in an exemplary embodiment of the curved display device according to the invention;

FIG. 6F is a schematic view illustrating a state in which a user recognizes an image displayed on an exemplary embodiment of the curved display device according the invention;

FIG. 7A is a schematic perspective view of a comparative example of a curved display device;

FIG. 7B is a schematic perspective view of a pixel and first and second alignment layers corresponding to the pixel in a comparative example of the curved display device according to the invention;

FIG. 7C is a schematic plan view of the first alignment layer shown in FIG. 7B ;

FIG. 7D is a schematic plan view of the second alignment layer shown in FIG. 7B ;

FIG. 7E is a plan view of overlapping areas between the first and second alignment layers and polarization plates in the curved display device shown in FIG. 7B ;

FIGS. 8A and 8B are views illustrating an exemplary embodiment of a method for forming first and second pretilt liquid crystals illustrated in FIG. 4A ;

FIG. 9 is a plan view of a pixel of an alternative exemplary embodiment of a curved display device according to the invention;

FIG. 10A is a cross-sectional view taken along line III-III′ of FIG. 9 .

FIG. 10B is a cross-sectional view taken along line IV-IV′ of FIG. 9 ;

FIG. 11 is a table illustrating an atomic force microscopy (“AFM”) image of Embodiment 1 and Comparative Example 1;

FIG. 12 is a table illustrating a distribution area of large-sized protrusions, each of which has a particle diameter of about 30 nanometers (nm) or more, in the AFM image of Embodiment 1 and Comparative Example 1; and

FIG. 13 is a table illustrating a distribution area of large-sized protrusions, each of which has a particle diameter of about 50 nm or more, in the AFM image of Embodiment 1 and Comparative Example 1.

The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.

“About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

Hereinafter, exemplary embodiments of the invention will be described in further detail with reference to the accompanying drawings.

FIG. 1A is a perspective view of an exemplary embodiment of a curved display device according to the invention, and FIG. 1B is a plan view of the curved display device illustrated in FIG. 1A .

FIG. 1C is a schematic cross-sectional view of an exemplary embodiment of the curved display device according to the invention;

Referring to FIGS. 1A to 1C , an exemplary embodiment of a curved display device 500 has a display area DA on which an image is displayed. The curved display device 500 has a curved shape. Thus, the curved display device 500 may display an image having improved three-dimensional effect, immersion, and presence through the display area DA having the curved shape.

In an exemplary embodiment, the curved display device 500 may include a display substrate 100 , an opposite substrate 300 , and a liquid crystal layer (e.g., LC of FIG. 3B ). The opposite substrate 300 is disposed opposite to the display substrate 100 and coupled to the display substrate 100 . The liquid crystal layer is disposed between the display substrate 100 and the opposite substrate 300 .

In such an embodiment, the curved display device 500 may further include other components in addition to the display substrate 100 and the opposite substrate 300 , but not being limited to the components. In one exemplary embodiment, for example, the curved display device 500 may further include a backlight assembly (not shown) that emits light toward the display substrate 100 and the opposite substrate 300 , but not being limited thereto.

In an exemplary embodiment, as shown in FIGS. 1A to 1C , the curved display device 500 may be curved in a predetermined direction, e.g., a first direction D 1 , on a plane, e.g., a plane defined by a non-curved sides of the curved display device 500 as shown in FIG. 1B . Thus, a portion or the whole of the display substrate 100 may have a shape that is curved in the first direction D 1 , and the display area DA may have a curved shape that is curved in the first direction D 1 . In such an embodiment, as shown in FIG. 1C , the display substrate 100 may have a first curvature radius R 1 . In such an embodiment, the opposite substrate 300 may have a curved shape, along with the display substrate 100 . In such an embodiment, the opposite substrate 300 may have a second curvature radius R 2 as shown in FIG. 1C . As described above, in an exemplary embodiment, where the display substrate 100 and the opposite substrate 300 are firmly coupled to each other, stress may be locally concentrated into the display substrate 100 and the opposite substrate 300 when the display substrate 100 and the opposite substrate 300 are curved in the first direction D 1 . In such an embodiment, an area in which a cell gap between the display substrate 100 and the opposite substrate 300 is non-uniform may occur on the display area DA to cause miss-alignment between the display substrate 100 and the opposite substrate 300 . That is, even though the display substrate 100 is precisely aligned with the opposite substrate 300 before the display substrate 100 and the opposite substrate are curved, the miss-alignment may occur after the display substrate 100 and the opposite substrate 300 are curved.

As illustrated in FIG. 4A , when the miss-alignment occurs, a pretilt direction of a first pretilt liquid crystal P 1 that is pretilted by a first alignment layer AL 1 may be different from that of a second pretilt liquid crystal P 2 that is pretilted by a second alignment layer AL 2 . If the pretilt direction of the first pretilt liquid crystals is different from that of the second pretilt liquid crystals overlapping the first pretilt liquid crystals, a rotation direction of the liquid crystal molecules may not be effectively defined by electric fields that are applied to the liquid crystal layer. Thus, a factor that deteriorates display quality such as a dark area may occur on the display area DA. In an exemplary embodiment, the curved display device 500 has a structure which effectively prevents the display quality from being deteriorated due to the above-described reasons.

FIG. 2 is a plan view of an exemplary embodiment of a pixel of the curved display device illustrated in FIG. 1A , FIG. 3A is a view of domains defined on the pixel illustrated in FIG. 2 , and FIG. 3B is a cross-sectional view taken along line I-I′ of FIG. 2 .

In an exemplary embodiment, the curved display device 500 includes a plurality of pixels. A pixel area PA, in which one pixel of the pixels is disposed, is illustrated in FIG. 2 . In such an embodiment, structure of the pixels are substantially the same as each other, the structure of the one pixel will be described in detail for convenience of description.

Referring to FIGS. 2, 3A, and 3B , an exemplary embodiment of the curved display device 500 includes the display substrate 100 , the opposite substrate 300 , and the liquid crystal layer LC disposed between the display substrate 100 and the opposite substrate 300 .

The opposite substrate 300 includes a first base substrate S 1 , a light blocking layer BM, a common electrode CE, and the first alignment layer AL 1 . In an exemplary embodiment, the first base substrate S 1 may be a transparent substrate, e.g., a glass substrate, having a light transmission property.

In an exemplary embodiment, the common electrode CE is disposed on the first base substrate S 1 to generate electric fields in the light crystal layer LC together with a pixel electrode PE. The light blocking layer BM blocks light. In such an embodiment, the light blocking layer BM extends along an area defined between a first sub pixel area PA 1 and a second sub pixel area PA 2 . The light blocking layer BM may extend along areas between domains adjacent to each other of first to eight domains DM 1 to DM 8 .

In an exemplary embodiment, the light blocking layer BM is disposed on the first base substrate S 1 as described above, but the invention is not limited thereto. In one alternative exemplary embodiment, for example, the light blocking layer BM may be disposed on a second base substrate S 2 of the display substrate 100 .

In an exemplary embodiment, the first alignment layer AL 1 may include a reactive mesogen RM. In such an embodiment, the first alignment layer AL 1 includes a first base layer PAL 1 and a first alignment formation layer PTL 1 disposed on the first base layer PAL 1 . A material of the first base layer PAL 1 is not limited to a specific material thereof. In one exemplary embodiment, for example, the first base layer PAL 1 may include or be formed of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane or polystyrene, mixture of the polymers, or a monomer of the polymers, but not being limited thereto. In an exemplary embodiment, the first base layer PAL 1 may include a material well known in the art as a base layer of an alignment layer.

In an alternative exemplary embodiment, the first alignment formation layer PTL 1 may not include the reactive mesogens RM that are polymerized with each other. In another alternative exemplary embodiment, the first alignment formation layer PTL 1 includes a small amount of reactive mesogens RM that are polymerized with each other when compared to that of a second alignment formation layer PTL 2 . Also, the first alignment formation layer PTL 1 may include a very small amount of reactive mesogens RM as an absolute amount. The term “reactive mesogen” may mean rephotocurable particles, i.e., a photo cross-linkable low-molecule or high-molecule copolymer. When light having a specific wavelength, for example, ultraviolet rays, are applied, chemical reaction such as polymerization reaction may occur in the reactive mesogen. The reactive mesogens RM are not specifically limited, but may be a reactive mesogen well known in the art. In one exemplary embodiment, for example, the reaction mesogens RM may include at least one of acrylate, methacrylate, epoxy, oxetane, vinyl ether, styrene, and derivatives thereof, but not being limited thereto.

The first alignment formation layer PTL 1 may not include substantial amount of the reactive mesogens RM as the described the above, thus the first alignment formation layer PTL 1 may not substantially pretilt the liquid crystal molecules adjacent to the first alignment layer AL 1 to have a predetermined pretilt angle with respect to a surface of the first base substrate S 1 . Thus, in such an embodiment, the liquid crystal molecules adjacent to the first base layer PAL 1 may not have specific directivity and be randomly disposed on the first alignment layer AL 1 In such an embodiment, when electrical fields are applied to the liquid crystal layer LC, the liquid crystal molecules adjacent to the first alignment layer AL 1 may be arranged on the first alignment layer AL 1 in a direction perpendicular to the first alignment layer AL 1 .

The small amount of reactive mesogens that are polymerized with each other may form first protrusions BU 1 . The first protrusions BU 1 may include first small-size protrusions SBU 1 and first large-size protrusions LBU 1 .

Each of the first protrusions BU 1 may have a particle size of, for example, about 1 nanometer (nm) or more. The first protrusions BU 1 may have a mean particle diameter of about 1 nm or more. Here, a representative value of the particle size may be above about 1 nm.

The first small-size protrusions SBU 1 and the first large-size protrusions LBU 1 may be defined or classified based on a particle diameter of about 30 nm. In one exemplary embodiment, for example, each of the first small-size protrusions SBU 1 may have a particle diameter of about 1 nm to about 30 nm Regarding the particle diameter, each of the first small-size protrusions SBU 1 may have a particle diameter of about 1 nm to about 30 nm, and the first small-size protrusions SBU 1 may have a mean particle diameter of about 1 nm to about 30 nm Here, a representative value of the first small-size protrusions SBU 1 may be in a range from about 1 nm to about 30 nm.

In such an embodiment, each of the first large-size protrusions LBU 1 may have a particle size of about 30 nm or more. Each of the first large-size protrusions LBU 1 may have a particle size of about 30 nm to about 1,000 nm Regarding the particle diameter, each of the first large-size protrusions LBU 1 may have a particle diameter of about 30 nm to about 1,000 nm, and the first large-size protrusions LBU 1 may have a mean particle diameter of about 30 nm to about 1,000 nm. Here, a representative value of the first large-size protrusions LBU 1 may be in a range from about 30 nm to about 1,000 nm.

The first small-size protrusions SBU 1 and the first large-size protrusions LBU 1 may be defined or classified based on a particle diameter of about 50 nm. In one exemplary embodiment, for example, each of the first small-size protrusions SBU 1 may have a particle diameter of about 1 nm to about 50 nm Regarding the particle diameter, each of the first small-size protrusions SBU 1 may have a particle diameter of about 1 nm to about 50 nm, and the first small-size protrusions SBU 1 may have a mean particle diameter of about 1 nm to about 50 nm Here, a representative value of the first small-size protrusions SBU 1 may range from about 1 nm to about 50 nm.

In such an embodiment, each of the first large-size protrusions LBU 1 may have a particle size of about 50 nm or more. Each of the first large-size protrusions LBU 1 may have a particle size of about 50 nm to about 1,000 nm Regarding the particle diameter, each of the first large-size protrusions LBU 1 may have a particle diameter of about 50 nm to about 1,000 nm, and the first large-size protrusions LBU 1 may have a mean particle diameter of about 50 nm to about 1,000 nm. Here, a representative value of the first large-size protrusions LBU 1 may range from about 50 nm to about 1,000 nm.

The first base layer PAL 1 and the first protrusions BU 1 will be described later in greater detail.

The first alignment layer AL 1 will be described later in greater detail with reference to FIGS. 4A to 4C .

In an exemplary embodiment, the display substrate 100 includes a second base substrate S 2 , a gate ling GL, a first data line DL 1 , a second data line DL 2 , a first thin film transistor TR 1 , a second thin film transistor TR 2 , a pixel electrode PE, a color filter CF and a second alignment layer AL 2 .

In such an embodiment, the second base substrate S 2 may be a transparent substrate, e.g., a glass substrate, having a light transmission property. The gate line GL is disposed on the second base substrate S 2 , and gate line GL is electrically connected to the first and second thin film transistors TR 1 and TR 2 to transmit a gate signal to the first and second thin film transistors TR 1 and TR 2 .

In an exemplary embodiment, the pixel area PA may include a first sub pixel area PA and a second sub pixel area PA 2 . In such an embodiment, the pixel electrode PE may include a first sub pixel electrode PE 1 disposed in the first sub pixel area PA 1 and a second sub pixel electrode PE 2 disposed in the second sub pixel area PA 2 .

The first and second data lines DL 1 and DL 2 are insulated from the gate line GL and disposed on the second base substrate S 2 . The first data line DL 1 transmits a first data signal, and the second data line DL 2 transmits a second data signal. In such an embodiment, the first data line DL 1 extends along a side of the first and second sub pixel electrodes PE 1 and PE 2 , and the second data line DL 2 extends along another side (e.g., opposite side) of the first and second sub pixel electrodes PE 1 and PE 2 .

The first thin film transistor TR 1 is electrically connected to the gate line GL, the first data line DL 1 and the first sub pixel electrode PE 1 . The first thin film transistor TFT 1 includes a first gate electrode GE 1 , a first active pattern AP 1 , a first source electrode SE 1 , and a first drain electrode DE 1 . The first gate electrode GE 1 may be branched from the gate line GL, and the first active pattern AP 1 may be disposed on the first gate electrode GE 1 with a first insulation layer L 1 therebetween. The first source electrode SE 1 is branched from the first data line DL 1 to contact the first active pattern APE and the first drain electrode DE 1 is spaced apart from the first source electrode SE 1 to contact the first active pattern AP 1 .

A second insulation layer L 2 is disposed on, e.g., covers, the first and second thin film transistors TR 1 and TR 2 . The color filter CF is disposed on the second insulation layer L 2 to filter light incident into the display substrate 100 through the second base substrate S 2 , thereby generating color light.

The second thin film transistor TR 2 is electrically connected to the gate line GL, the second data line DL 2 , and the second sub pixel electrode PE 2 . The second thin film transistor TFT 2 includes a second gate electrode GE 2 , a second active pattern AP 2 , a second source electrode SE 2 , and a second drain electrode DE 2 . In such an embodiment, the second thin film transistor TR 2 has a structure similar to that of the first thin film transistor TR 1 , and any repetitive detailed descriptions of the second thin film transistor TR 2 will be omitted.

In such an embodiment, the first and second thin film transistors TR 1 and TR 2 may be turned on by the gate signal to provide the first data signal to the first sub pixel electrode PE 1 through the first thin film transistor TR 1 and provide the second data signal, which is different from the first data signal, to the second sub pixel electrode PE 2 through the second thin film transistor TR 2 . Thus, the first and second sub pixel electrodes PE 1 and PE 2 are driven by the data signals different from each other to display gray scales different from each other on the first and second sub pixel areas PA 1 and PA 2 .

In such an embodiment, the first sub pixel electrode PE 1 includes a first horizontal stem part HS 1 , a first vertical stem part VS 1 , and first to fourth branch parts B 1 , B 2 , B 3 and B 4 . The first horizontal stem part HS 1 extends in the first direction D 1 to cross the first sub pixel area PA 1 . The first vertical stem part VS 1 extends in a second direction D 2 to cross the first sub pixel area PA 1 , and the first vertical stem part VS 1 is connected to the first horizontal stem part HS 1 . In such an embodiment, the first direction D 1 may cross the second direction D 2 . In one exemplary embodiment, for example, the first direction D 1 may be substantially perpendicular to the second direction D 2 .

The first branch parts B 1 are branched from the first horizontal stem part HS 1 or the first vertical stem part VS 1 . The first horizontal branch parts B 1 are spaced apart from each other. Thus, a slit ST may be defined between two first branch parts B 1 adjacent to each other of the first branch parts B 1 . In such an embodiment, each of the first branch parts B 1 may extend in a third direction D 3 that is inclined with respect to the first and second directions D 1 and D 2 on a plane. In such an embodiment, an acute angle defined by the third direction D 2 and each of the first and second directions D 1 and D 2 may be in a range from about 40 degrees to about 50 degrees on a plane.

The second branch parts B 2 are branched from the first horizontal stem part HS 1 or the first vertical stem part VS 1 . In such an embodiment, each of the second branch parts B 2 may extend in a fourth direction D 4 that is inclined with respect to the first and second directions D 1 and D 2 on a plane. In such an embodiment, the fourth direction D 4 may cross the third direction D 3 on a plane, and an acute angle defined by the fourth direction D 4 and each of the first and second directions D 1 and D 2 may be in a range from about 40 degrees to about 50 degrees on a plane.

The third branch parts B 3 are branched from the first horizontal stem part HS 1 or the first vertical stem part VS 1 . The fourth branch parts D 4 are branched from the first horizontal stem part HS 1 or the first vertical stem part VS 1 . In such an embodiment, each of the third branch parts B 3 extend in the fourth direction D 4 on a plane, and the fourth branch parts B 4 may extend in the third direction D 3 on a plane.

The second sub pixel electrode PE 2 includes a second horizontal stem part HS 2 , a second vertical stem part VS 2 , and fifth to eighth branch parts B 5 , B 6 , B 7 , and B 8 . In such an embodiment, the second sub pixel electrode PE 2 may have a size greater than that of the first sub pixel electrode PE 1 . In such an embodiment, the second sub pixel electrode PE 2 has a structure similar to that of the first sub pixel electrode PE 1 , and any repetitive detailed descriptions of the structure of the second sub pixel electrode PE 2 will be omitted.

In an exemplary embodiment, where the first to eighth branch parts B 1 to B 8 have the above-described structure, the first to fourth domains DM 1 , DM 2 , DM 3 and DM 4 may be defined on the first sub pixel area PA 1 , and fifth to eighth domains DM 5 , DM 6 , DM 7 and DM 8 may be defined on the second sub pixel area PA 2 .

In such an embodiment, the first to eighth domains DM 1 to DM 8 may be defined to one-to-one correspond to the areas on which the first to eighth branch parts B 1 to B 8 are disposed. When electric fields are generated between the pixel electrode PE and the common electrode CE, the liquid crystal molecules of the liquid crystal layer LC are aligned in a first liquid crystal alignment direction DR 1 on the first domain DM. In such an embodiment, the liquid crystal molecules are aligned to one-to-one correspond to second to fourth liquid crystal alignment directions DR 2 , DR 3 , and DR 4 on the second to fourth domains DM 2 , DM 3 and DM 4 in response to the electric fields. Here, the first to fourth liquid crystal alignment directions DR 1 , DR 2 , DR 3 and DR 4 may be different from each other.

Like the directions in which the liquid crystal molecules are aligned on the first to fourth domains DM 1 to DM 4 , the liquid crystal molecules are aligned to one-to-one correspond to the first to fourth liquid crystal alignment directions DR 1 , DR 2 , DR 3 and DR 4 on the fifth to eighth domains DM 5 to DM 8 .

In such an embodiment, the first and second domains DM 1 and DM 2 are arranged (e.g., disposed adjacent to each other) in the first direction DE the third and fourth domains DM 3 and DM 4 are arranged in the first direction DE the first and third domains DM 1 and DM 3 are arranged in the second direction D 2 , and the second and fourth domains DM 2 and DM 4 are arranged in the second direction D 2 .

The second alignment layer AL 2 aligns the liquid crystal molecules of the liquid crystal layer LC. In an exemplary embodiment, the second alignment layer AL 2 may include a material for fixing the liquid crystal molecules adjacent to the second alignment layer AL 2 of the liquid crystal molecules to the second alignment layer AL 2 . In such an embodiment, the second alignment layer AL 2 may include reactive mesogens RM that are coupled to the liquid crystal molecules to pretilt the liquid crystal molecules.

In an exemplary embodiment, the second alignment layer AL 2 includes a second base layer PAL 2 and a second alignment formation layer PTL 2 disposed on the second base layer PAL 2 . The second base layer PAL 2 is not limited to a specific material, but may include any well-known material for forming the base substrate. In one exemplary embodiment, for example, the second base layer PAL 2 may include or be formed of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane, or polystyrene, mixture of the polymers or a monomer of the polymers, but not being limited thereto.

The second alignment formation layer PTL 2 includes reactive mesogens RM that are polymerized with each other. The second alignment formation layer PTL 2 may allow the liquid crystal molecules adjacent to the second alignment layer ALN 2 to substantially pretilt. In an exemplary embodiment, an amount of polymerized reactive mesogens RM in the second alignment formation layer PTL 2 may greater than an amount of polymerized reactive mesogens RM in the first alignment formation layer PTL 1 . Thus, the second alignment formation layer PTL 2 may pretilt the liquid crystal molecules adjacent to the second base layer PAL 2 such that the liquid crystal molecules are substantially tilted at a predetermined angle with respect to a surface of the second base substrate S 2 .

The reactive mesogens RM are not specifically limited a specific material, but may be a reactive mesogen well known in the art or widely used in the art. In one exemplary embodiment, for example, the reaction mesogens RM may include at least one of acrylate, methacrylate, epoxy, oxetane, vinyl ether, styrene, and derivatives thereof, but not being limited thereto.

In an exemplary embodiment, as shown in FIG. 4A , the reactive mesogens may define second protrusions BU 2 of the second alignment formation layer PTL 2 . The second protrusions BU 2 may include second small-size protrusions SBU 2 and second large-size protrusions LBU 2 .

Each of the second protrusions BU 2 may have a particle size of, for example, about 1 nm or more. The second protrusions BU 2 may have a mean particle diameter of about 1 nm or more. In an exemplary embodiment, a representative value of the second protrusions BU 2 may be above about 1 nm.

The second small-size protrusions SBU 2 and the second large-size protrusions LBU 2 may be defined or classified based on a particle diameter of about 30 nm. In one exemplary embodiment, for example, each of the second small-size protrusions SBU 2 may have a particle diameter of about 1 nm to about 30 nm Regarding the particle diameter, each of the second small-size protrusions SBU 2 may have a particle diameter of about 1 nm to about 30 nm, and the second small-size protrusions SBU 2 may have a mean particle diameter of about 1 nm to about 30 nm. In such an embodiment, a representative value of the second small-size protrusions SBU 2 may be in a range from about 1 nm to about 30 nm.

In such an embodiment, each of the second large-size protrusions LBU 2 may have a particle size of about 30 nm or more. Each of the second large-size protrusions LBU 2 may have a particle size of about 30 nm to about 1,000 nm Regarding the particle diameter, each of the second large-size protrusions LBU 2 may have a particle diameter of about 30 nm to about 1,000 nm, and the second large-size protrusions LBU 2 may have a mean particle diameter of about 30 nm to about 1,000 nm. In such an embodiment, a representative value of the second small-size protrusions SBU 2 may in a range from about 30 nm to about 1,000 nm.

The second small-size protrusions SBU 2 and the second large-size protrusions LBU 2 may be defined or classified based on a particle diameter of about 50 nm. In one exemplary embodiment, for example, each of the second small-size protrusions SBU 2 may have a particle diameter of about 1 nm to about 50 nm Regarding the particle diameter, each of the second small-size protrusions SBU 2 may have a particle diameter of about 1 nm to about 50 nm, and the second small-size protrusions SBU 2 may have a mean particle diameter of about 1 nm to about 50 nm. In such an embodiment, a representative value of the second small-size protrusions SBU 2 may be in a range from about 1 nm to about 50 nm.

In such an embodiment, each of the second large-size protrusions LBU 2 may have a particle size of about 50 nm or more. Each of the second large-size protrusions LBU 2 may have a particle size of about 50 nm to about 1,000 nm Regarding the particle diameter, each of the second large-size protrusions LBU 2 may have a particle diameter of about 50 nm to about 1,000 nm, and the second large-size protrusions LBU 2 may have a mean particle diameter of about 50 nm to about 1,000 nm. In such an embodiment, a representative value of the second large-size protrusions LBU 2 may be in a range from about 50 nm to about 1,000 nm.

Hereinafter, distribution of the first protrusions BU 1 on the first base layer PAL 1 and distribution of the second protrusions BU 2 on the second base layer PAL 2 will be described in greater detail.

In an exemplary embodiment, as described above, the small of reactive mesogens that are polymerized with each other may form the first protrusions BU 1 on the first base layer PAL 1 . In such an embodiment, the first protrusions BU 1 may include the first small-size protrusions SBU 1 and the first large-size protrusions LBU 1 . In such an embodiment, the first base layer PAL 1 may include a first overlapping area that overlaps the first large-size protrusions LBU 1 and a first non-overlapping area that does not overlap the first large-size protrusions LBU 1 .

In such an embodiment, the reactive mesogens that are polymerized with each other may define the second protrusions BU 2 on the second base layer PAL 2 . In such an embodiment, the second protrusions BU 2 may include the second small-size protrusions SBU 2 and the second large-size protrusions LBU 2 . In such an embodiment, the second base layer PAL 2 may include a second overlapping area that overlaps the second large-size protrusions LBU 2 and a second non-overlapping area that does not overlap the second large-size protrusions LBU 2 .

In one exemplary embodiment, for example, the first overlapping area and the first non-overlapping area, and the second overlapping area and the second non-overlapping area may be divided by a boundary between the area on which the large-side protrusions are disposed and the area on which the large-size protrusions are not disposed, when viewed in a fifth direction (e.g., D 5 of FIG. 6B ).

In the following descriptions, the first overlapping area may have a surface area that corresponds to a mean value or reprehensive value of areas extracted from any unit area of the first base layer PAL 1 as well as the entire surface area of the first overlapping area on the first base layer PAL 1 . The first non-overlapping area may have a surface area that corresponds to a mean value or reprehensive value of areas extracted from any unit area of the first base layer PAL 1 as well as the entire surface area of the first non-overlapping area on the first base layer PAL 1 The second overlapping area may have a surface area that corresponds to a mean value or reprehensive value of areas extracted from any unit area of the second base layer PAL 2 as well as the entire surface area of the second overlapping area on the second base layer PAL 2 .

Hereinafter, an exemplary embodiment, in which each of the first and second large-size protrusions LBU 1 and LBU 2 has a particle diameter of about 30 nm to about 1,000 nm, will be described.

When the each of the first and second large-size protrusions LBU 1 and LBU 2 has a particle diameter of about 30 nm to about 1,000, the first and second overlapping areas in an exemplary embodiment of the curved display device 500 according to the invention may have a relationship that is expressed by the following Inequation 1.

0<surface area of first overlapping area/surface area of second overlapping area≤⅘  Inequation 1:

When the surface area of first overlapping area/surface area of second overlapping area exceeds ⅘, the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The first overlapping area may have a surface area less than that of the first non-overlapping area. The first and second overlapping areas in an exemplary embodiment of the curved display device 500 according to the invention may have a relationship that is expressed as the following Inequation 2.

0<surface area of first overlapping area/surface area of first non-overlapping area< 5/10  Inequation 2:

When the surface area of first overlapping area/surface area of first non-overlapping area is equal to or greater than 5/10, the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The first overlapping area may have a surface area that is greater than 0 nm 2 and equal to or less than 3.5×10 5 nm 2 in a unit area (1.0×10 6 nm 2 ) of a surface of the first base layer PAL 1 that is, in a unit area of 1.0×10 6 nm 2 defined on the first base layer PAL 1 When the first overlapping area has a surface area that is greater than 3.5×10 5 nm 2 in the unit area (1.0×10 6 nm 2 ) of the surface of the first base layer PAL 1 the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The second overlapping area may have a surface area that is equal to or greater than 3.0×10 5 nm 2 and equal to or less than 1.0×10 6 nm 2 in a unit area (1.0×10 6 nm 2 ) of a surface of the second base layer PAL 2 . When the second overlapping area has a surface area that is less than 3.0×10 5 nm 2 in the unit area (1.0×10 6 nm 2 ) of the surface of the second base layer PAL 2 , the number of second large-size protrusions LBU 2 may be too less to allow the liquid crystal molecules adjacent to the first alignment layer AL 1 to be effectively tilted by the second alignment layer AL 2 .

The amount of the reactive mesogens in the second alignment layer AL 2 may be greater than the amount of the reactive mesogens in the first alignment layer AL 1 . Thus, the number of the first large-size protrusions LBU 1 may be less than the number of the second large-size protrusions LBU 2 .

Hereinafter, an exemplary embodiment in which each of the first and second large-size protrusions LBU 1 and LBU 2 has a particle diameter of about 50 nm to about 1,000 nm will be described.

When the each of the first and second large-size protrusions LBU 1 and LBU 2 has a particle diameter of about 50 nm to about 1,000, the first and second overlapping areas in an exemplary embodiment of the curved display device 500 according to the invention may have a relationship that is expressed by the following Inequation 3.

0<surface area of first overlapping area/surface area of second overlapping area≤½  Inequation 3:

When the surface area of first overlapping area/surface area of second overlapping area exceeds ½, the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The first overlapping area may have a surface area less than that of the first non-overlapping area. The first and second overlapping areas in an exemplary embodiment of the curved display device 500 according to the invention may have a relationship that is expressed by the following Inequation 4.

0<surface area of first overlapping area/surface area of first non-overlapping area≤ 1/10  Inequation 4:

When the surface area of first overlapping area/surface area of first non-overlapping area exceeds 1/10, the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The first overlapping area may have a surface area that is greater than 0 nm 2 and equal to or less than 0.3×10 5 nm 2 in the unit area (1.0×10 6 nm 2 ) of the surface of the first base layer PAL 1 When the first overlapping area has a surface area that is greater than 0.3×10 5 nm 2 in the unit area (1.0×10 6 nm 2 ) of the surface of the first base layer PAL 1 , the liquid crystal molecules adjacent to the first alignment layer AL 1 may be tilted to generate a dark area on which light is not seen, as described below with reference to FIG. 7A to 7E .

The second overlapping area may have a surface area that is equal to or greater than 0.4×10 5 nm 2 and equal to or less than 1.0×10 6 nm 2 in a unit area (1.0×10 6 nm 2 ) of a surface of the second base layer PAL 2 . If the number of second large-size protrusions LBU 2 is substantially low, the liquid crystal molecules adjacent to the first alignment layer AL 1 may not be effectively tilted by the second alignment layer AL 2 .

In an exemplary embodiment, as described above, the liquid crystal molecules are aligned by the electric fields in the state where the liquid crystal molecules are pretilted by the first and second alignment layers AL 1 and AL 2 , such that a response time of the curved display device 500 may be improved.

FIG. 4A is a cross-sectional view taken along line II-II′ of FIG. 2 , FIG. 4B is an enlarged view of a first pretilt liquid crystal illustrated in FIG. 4A , and FIG. 4C is a view of a second pretilt liquid crystal illustrated in FIG. 4A .

Referring to FIGS. 4A, 4B and 4C , a cell gap CG is defined between the display substrate 100 and the opposite substrate 300 . The liquid crystal layer LC including the liquid crystal molecules may be disposed between, e.g., filled into, the cell gap CG. When the liquid crystal molecules adjacent to the first alignment layer AL 1 of the liquid crystal molecules are defined as first pretilt liquid crystals P 1 , and the liquid crystal molecules, which are pretilted by the second alignment layer AL 2 , of the liquid crystal molecules are defined as second pretilt liquid crystals P 2 , the first alignment layer AL 1 may not substantially pretilt the first pretilt liquid crystals P 1 . The first pretilt liquid crystals P 1 may have a first pretilt-angle a 1 with respect to the first alignment layer AL 1 . The second alignment layer AL 2 aligns the second pretilt liquid crystals P 2 at a second pretilt-angle a 2 .

In such an embodiment, when a normal line NL of the first alignment layer AL 1 , a first straight line SL 1 on the first alignment layer AL 1 and a first long axis L 11 of the first pretilt liquid crystals P 1 are defined as illustrated in FIG. 4B , the first pretilt-angle a 1 may be defined as an angle between the first long axis L 11 and the first straight line SL 1 .

In such an embodiment, when a normal line NL of the second alignment layer AL 2 , a second straight line SL 2 on the second alignment layer AL 2 and a second long axis L 12 of the second pretilt liquid crystals P 2 are defined as illustrated in FIG. 4C , the second pretilt-angle a 2 may be defined as an angle between the second long axis L 12 and the second straight line SL 2 .

In one exemplary embodiment, for example, the second pretilt-angle a 2 may be a value of each of the pretilt-angles of the liquid crystal molecules adjacent to the second alignment layer AL 2 , a mean value of the pretilt-angles of the liquid crystal molecules adjacent to the second alignment layer AL 2 , or a representative value of the pretilt-angles of the liquid crystal molecules adjacent to the second alignment layer AL 2 . The second pretilt-angle a 2 may be in a range of about 80° to about 90°. The second pretilt-angle a 2 may be in a range of about 80° to about 89°. The second pretilt-angle a 2 may be greater 80° and less than 88° so that the second pretilt-angle a 2 is different from the first pretilt-angle a 1 .

The first pretilt-angle a 1 may be different from the second pretilt-angle a 2 and greater than the second pretilt-angle a 2 . In one exemplary embodiment, for example, the first pretilt-angle a 1 may be a value of each of the pretilt-angles of the liquid crystal molecules adjacent to the first alignment layer AL 1 , a mean value of the pretilt-angles of the liquid crystal molecules adjacent to the first alignment layer AL 1 , or a representative value of the pretilt-angles of the liquid crystal molecules adjacent to the first alignment layer ALL The first pretilt-angle a 1 may range of about 88° to about 90°. The first pretilt-angle a 1 may range of about 89° to about 90°. The first pretilt-angle a 1 may be set to be greater than the second pretilt-angle a 2 in the range of about 88° to about 90°. In an exemplary embodiment, where the second pretilt-angle a 2 is set to be an angle of about 80°, 85°, 86° or 89°, the first pretilt-angle a 1 may be set to be an angle of about 89.5° or about 90° that is greater than that of the second pretilt-angle a 2 .

In such an embodiment, the second pretilt-angle a 2 may be less than the first pretilt-angle a 1 . In one exemplary embodiment, for example, the first pretilt-angle a 1 may be about 89.8°, and the second pretilt-angle a 2 may be about 88°. When the second pretilt-angle a 2 is less than the first pretilt-angle a 1 , the tendency in which the liquid crystal molecules filled into the cell gap CG behave by the second pretilt liquid crystals P 2 in response to the electric fields acting on the cell gap CG may be stronger than that in which the liquid crystal molecules behave by the first pretilt liquid crystals P 1 .

In an exemplary embodiment, when a first portion of the liquid crystal molecules that are aligned parallel to a direction of the first pretilt liquid crystals P 1 in response to the electric fields is defined as first liquid crystal molecules P 1 - 1 , and a second portion of the liquid crystal molecules that are aligned parallel to a direction of the second pretilt liquid crystals P 2 in response to the electric fields is defined as second liquid crystal molecules P 2 - 1 , an amount of second liquid crystal molecules P 2 - 1 is greater than that of first liquid crystal molecules P 1 - 1 .

Thus, in an exemplary embodiment, where the cell gap CG is divided into a first space A 1 and a second space A 2 , which are disposed in a direction perpendicular to the second base substrate S 2 , when the first space A 1 is defined as a space in which the first liquid crystal molecules P 1 - 1 are filled, and the second space A 2 is defined as a space in which the second liquid crystal molecules P 2 - 1 are filled, the second space A 2 may be greater than the first space A 1 , e.g., the second space A 2 have a thickness (or a width on a cross-section) greater than that of the first space A 1 .

The first alignment layer AL 1 may not substantially include the first reactive mesogens, and the second alignment layer AL 2 may substantially include the second reactive mesogens for fixing the liquid crystal molecules to the second alignment layer A 12 . Also, an amount of second reactive mesogens per unit area of the second alignment layer AL 2 may be greater than that of first reactive mesogens per unit area of the first alignment layer AL 1 . Thus, if an amount of second reactive mesogens is greater than that of first reactive mesogens, an amount of second pretilt liquid crystals P 2 fixed to the second alignment layer AL 2 by the second reactive mesogens may be less than that of first pretilt liquid crystals P 1 . Accordingly, in an exemplary embodiment, the amount of second liquid crystal molecules P 2 - 1 is greater than that of first liquid crystal molecules P 1 - 1 .

In an exemplary embodiment, an amount of second reactive mesogens respectively coupled or adjacent to the second pretilt liquid crystals P 2 may be greater than that of first reactive mesogens respectively coupled or adjacent to the first pretilt liquid crystals P 1 . As a result, a force by which each of the second pretilt liquid crystals P 2 is pulled toward a surface of the second alignment layer AL 2 by the second reactive mesogens is greater than that by which each of the first pretilt liquid crystals P 1 is pulled toward a surface of the first alignment layer AL 1 by the first reactive mesogens. Thus, in such an embodiment, the second pretilt-angle a 2 is greater than the first pretilt-angle a 1 .

As described above with reference to FIGS. 1A to 1C , as the curved display device is curved to have a curved shape, the miss-alignment between the display substrate 100 and the opposite substrate 300 may occur. When the miss-alignment occurs, a pretilt direction of the first pretilt liquid crystals P 1 may be different from that of the second pretilt liquid crystals P 2 that overlap the first pretilt liquid crystals P 1 . In an exemplary embodiment, where the amount of first pretilt liquid crystals P 1 is less than that of second pretilt liquid crystals P 2 , an amount of liquid crystal molecules that are aligned in direction opposite to each other on the area on which the miss-alignment occurs may be reduced, such that an occurrence of a factor that deteriorates the display quality such as the dark area in the curved display device 50 may be reduced.

FIGS. 5A to 5D are photographs illustrating brightness of first to eight domains according to the first and second pretilt-angles. FIG. 5A illustrates brightness of the domains when the first pretilt-angle (see reference symbol a 1 of FIG. 4B ) that is described with reference to FIG. 4B is about 89°, and the second pretilt-angle (see reference numeral a 2 of FIG. 4B ) that is described with reference to FIG. 4C is about 89°. In this case, a dark area having a band shape in the second direction (see reference numeral D 2 of FIG. 3A ) may occur on the domains to deteriorate the display quality of the curved display device.

FIG. 5B illustrates brightness of the domains when the first pretilt-angle is about 89.5°, and the second pretilt-angle is about 88°. In this case, a dark area having a band shape may occur on the domains. Here, a visible degree (e.g., visible size) of the dark area of FIG. 5B may be less than that of the dark area of FIG. 5A .

FIG. 5C illustrates brightness of the domains when the first pretilt-angle is about 89.8°, and the second pretilt-angle is about 89.0°. In this case, a dark area having a band shape does not substantially occur on the domains. That is, each of the domains may have substantially uniform brightness.

FIG. 5D illustrates brightness of the domains when the first pretilt-angle is about 90°, and the second pretilt-angle is about 89°. In this case, a dark area having a band shape does not substantially occur on the domains. That is, each of the domains may have substantially uniform brightness.

As shown in FIGS. 5A to 5D , a visible degree of the dark area on the domains may be less than that of the dark area when the second pretilt-angle is less than the first pretilt-angle. In an exemplary embodiment, where the second pretilt-angle is less than the first pretilt-angle, when a difference between the second pretilt-angle and the first pretilt-angle may be about 0.4° to about 1.2°, the visible degree of the dark area on the domains may be minimized to realize substantially uniform brightness on the domains.

In such an embodiment, where the difference between the second pretilt-angle and the first pretilt-angle is in the range of about 0.4° to about 1.2°, when the first pretilt-angle is about 89.6° to about 90.0°, the visible degree of the dark area on the domains may be minimized to realize uniform brightness on the domains.

FIG. 6A is a schematic perspective view of an exemplary embodiment of the curved display device according to the invention. FIG. 6B is a schematic perspective view of the pixel and the first and second alignment layers corresponding to the pixel of an exemplary embodiment of the curved display device according to the invention. FIG. 6C is a schematic plan view of the first alignment layer shown in FIG. 6B . FIG. 6D is a schematic plan view of the second alignment layer shown in FIG. 6B . FIG. 6E is a schematic plan view of an overlapping area between the first and second alignment layers, a lower polarization plate and an upper polarization plate in an exemplary embodiment of the curved display device according to the invention. FIG. 6F is a schematic view illustrating a state in which a user recognizes an image displayed on an exemplary embodiment of the curved display device according to the invention.

Referring to FIGS. 4A and 6A to 6D , the second alignment layer AL 2 includes lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 and L_AA 4 . The lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 and L_AA 4 include a first lower alignment area L_AA 1 , a second lower alignment area L_AA 2 , a third lower alignment area L_AA 3 and a fourth lower alignment area L_AA 4 . The lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 and L_AA 4 may correspond to overlap the domains DM 1 , DM 2 , DM 3 and DM 4 in a fourth direction D 4 that is a normal direction of the pixel PX and a seventh direction D 7 that is opposite to the sixth direction D 6 .

The first domain DM 1 , the second domain DM 2 , the third domain DM 3 and the fourth domain DM 4 may one-to-one correspond to the first lower alignment area L_AA 1 , the second lower alignment area L_AA 2 , the third lower alignment area L_AA 3 and the fourth lower alignment area L_AA 4 . The second pretilt liquid crystal molecules P 2 may be pretilted by the second reactive mesogens that are polymerized with each other on each of the first to fourth lower alignment areas L_AA, L_AA 2 , L_AA 3 and L_AA 4 . When the electrical fields are generated in the liquid crystal layer LC, the second pretilt liquid crystals P 2 and the second pretilt liquid crystal molecules P 2 - 1 may be quickly aligned in a parallel direction than the liquid crystal molecules that are not pretilted. That is, the liquid crystal molecules may be quickly rearranged from a vertically aligned state to a parallelly aligned state.

When the electrical fields are applied to the liquid crystal layer LC, the second pretilt first liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 may be aligned in a direction parallel to an extension direction of the first branch parts (B 1 of FIG. 2 ) on the first lower alignment area L_AA 1 . Here, the extension direction of the first branch parts may be substantially parallel to the first liquid crystal alignment direction DR 1 . The first liquid crystal alignment direction DR 1 may represent a mean direction of parallelly aligned directions when the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are parallelly aligned on the first lower alignment area L_AA 1 .

Similarly, when the electric fields are applied to the liquid crystal layer LC, the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are aligned in a second liquid crystal alignment direction DR 2 on the second lower alignment area L_AA 2 , the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are aligned in a third liquid crystal alignment direction DR 3 on the third lower alignment area L_AA 3 , and the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are aligned in a fourth liquid crystal alignment direction DR 4 on the fourth lower alignment area L_AA 4 . The second liquid crystal alignment direction D 2 may represent a mean direction of parallelly aligned directions when the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are parallelly aligned on the second lower alignment area L_AA 2 . The third liquid crystal alignment direction D 3 may represent a mean direction of parallelly aligned directions when the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are parallelly aligned on the third lower alignment area L_AA 3 . The fourth liquid crystal alignment direction D 2 may represent a mean direction of parallelly aligned directions when the second pretilt liquid crystals P 2 and the second liquid crystal molecules P 2 - 1 are parallelly aligned on the fourth lower alignment area L_AA 4 .

The first alignment layer AL 1 includes upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 and U_AA 4 . The upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 and U_AA 4 include a first upper alignment area U_AA 1 , a second upper alignment area U_AA 2 , a third upper alignment area U_AA 3 , and a fourth upper alignment area U_AA 4 . The upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 and U_AA 4 may correspond to overlap the domains DM 1 , DM 2 , DM 3 and DM 4 in a sixth direction D 6 and seventh direction D 7 .

In such an embodiment, the first alignment layer AL 1 includes the first reactive mesogens. In such an embodiment, an amount of first reactive mesogens may be less than that of second reactive mesogens as described above. In another exemplary embodiment, the amount of first reactive mesogens may be negligibly less in comparison to that of second reactive mesogens. Thus, the amount of first pretilt liquid crystals P 1 on each of the first, second, third and fourth upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 and U_AA 4 may be negligibly less in comparison to that of second pretilt liquid crystals P 2 . Also, the amount of first liquid crystal molecules P 1 - 1 may be negligibly less in comparison to that of second pretilt liquid crystal molecules P 2 - 1 . When a degree of an arrangement of the second liquid crystal molecules P 2 - 1 of the first lower alignment area L_AA 1 in the first liquid crystal alignment direction DR 1 is defined as a first scalar value, and a degree of an arrangement of the first liquid crystal molecules P 1 - 1 of the first upper alignment area U_AA 1 in the first liquid crystal alignment direction DR 1 is defined as a second scalar value, the second scalar value may be significantly less than the first scalar value. Since the first liquid crystal molecules P 1 - 1 are not substantially pretilted, a parallelly aligned rate of the first liquid crystal molecules P 1 - 1 on the first upper alignment area U_AA 1 may be substantially, e.g., significantly, less than that of the second liquid crystal molecules P 2 - 1 on the first lower alignment area L_AA 1 . Also, the number of first liquid crystal molecules P 1 - 1 that are aligned in parallel to the first liquid crystal alignment direction DR 1 may be significantly less than that of second liquid crystal molecules P 2 - 1 that are aligned in parallel to the first liquid crystal alignment direction DR 1 .

Similarly, when the electric fields are applied to the liquid crystal layer LC, the first liquid crystal molecules P 1 - 1 may be weakly aligned in the second liquid crystal alignment direction DR 2 on the second upper alignment area U_AA 2 , be weakly aligned in the third liquid crystal alignment direction DR 3 on the third upper alignment area U_AA 3 , and be weakly aligned in the fourth liquid crystal alignment direction DR 4 on the fourth upper alignment area U_AA 4 .

Referring to FIGS. 6A to 6E , when viewed in the fifth direction D 5 , the first and second alignment layers AL 1 and AL 2 have overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 , and OVA 6 which overlap each other. The overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 and OVA 6 include a first overlapping area OVA 1 , a second overlapping area OVA 2 , a third overlapping area OVA 3 , a fourth overlapping area OVA 4 , a fifth overlapping area OVA 5 , and a sixth overlapping area OVA 6 .

When the electric fields are applied to the liquid crystal layer LC, an optical axis direction of the liquid crystal layer LC may be equal to a mean value of the parallelly aligned direction of the second liquid crystal molecules P 2 - 1 on the lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 , and L_AA 4 and the parallelly aligned direction of the first liquid crystal molecules P 1 - 1 on the upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 , and U_AA 4 .

The second overlapping area OVA 2 may be an area on which the second lower alignment area L_AA 2 and the first upper alignment area U_AA 1 overlap each other. Since the first liquid crystal molecules P 1 - 1 are not substantially pretilted and the second liquid crystal molecules P 2 - 1 are pretilted, a parallelly aligned rate of the first liquid crystal molecules P 1 - 1 on the first overlapping area OVA 1 may be significantly less than that of the second liquid crystal molecules P 2 - 1 . Also, the number of first liquid crystal molecules P 1 - 1 that are aligned in parallel to the second liquid crystal alignment direction DR 2 may be significantly less than that of second liquid crystal molecules P 2 - 1 that are aligned in parallel to the first liquid crystal alignment direction DR 1 .

Thus, when the electric fields are applied to the liquid crystal layer LC, the optical axis direction of the liquid crystal layer LC on the second overlapping area OVA 2 may be substantially parallel to the second liquid crystal alignment direction DR 2 . Similarly, when the electric fields are applied to the liquid crystal layer LC, an optical axis direction of the liquid crystal layer LC on the fifth overlapping area OVA 5 may be substantially parallel to the fourth liquid crystal alignment direction DR 4 .

The parallelly aligned direction of the second liquid crystal molecules P 2 - 1 on the first overlapping area OVA 1 may be the substantially same as that of the first liquid crystal molecules P 1 - 1 . Thus, the optical axis direction of the liquid crystal layer LC on the first overlapping area OVA 1 is substantially parallel to the first liquid crystal alignment direction DR 1 . Similarly, an optical axis direction of the liquid crystal layer LC on the third overlapping area OVA 3 is substantially parallel to the second liquid crystal alignment direction DR 2 , an optical axis direction of the liquid crystal layer LC on the fourth overlapping area OVA 4 is substantially parallel to the third liquid crystal alignment direction DR 3 , and an optical axis direction of the liquid crystal layer LC on the sixth overlapping area OVA 6 is substantially parallel to the fourth liquid crystal alignment direction DR 4 .

The lower polarization plate POL 1 has a first transmission axis PA 1 , and the upper polarization plate POL 2 has a second transmission axis PA 2 . The first transmission axis PA 1 and the second transmission axis PA 2 are perpendicular to each other. In one exemplary embodiment, for example, when the first transmission axis PA 1 is parallel to the second direction D 2 , the second transmission axis PA 2 is parallel to the first direction D 1 . For convenience of illustration, FIG. 6E show the lower and upper polarization plates POL 1 and POL 2 , each of which has a size relatively less than that of each of the first and second alignment layers AL 1 and AL 2 .

Referring to FIGS. 6A to 6F , the optical axis direction of the liquid crystal layer LC is not substantially parallel to the directions of the first transmission axis PA 1 of the lower polarization plate POL 1 and the second transmission axis PA 2 of the upper polarization plate POL 2 within each of the first, second, third, fourth, fifth and sixth overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 , and OVA 6 in an exemplary embodiment of the curved display device 500 according to the invention. Thus, the user USER may see light passing through the first, second, third, fourth, fifth, and sixth overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 , and OVA 6 .

FIG. 7A is a schematic perspective view of a comparative example of a curved display device. FIG. 7B is a schematic perspective view of a pixel and first and second alignment layers corresponding to the pixel, which are included in a comparative example the curved display device. FIG. 7C is a schematic plan view of the first alignment layer shown in FIG. 7B . FIG. 7D is a schematic plan view of the second alignment layer shown in FIG. 7B . FIG. 7E is a schematic plan view of overlapping areas between the first and second alignment layers and polarization plates in the curved display device shown in FIG. 7B .

Referring to FIGS. 7A to 7E , a comparative example of a curved display device 1000 includes a first alignment layer AL 1 including reactive mesogens that are polymerized with each other and a second alignment layer AL 2 including reactive mesogens that are polymerized with each other. The first and second alignment layers AL 1 and AL 2 may include the reactive mesogens having the substantially same amount as each other. Thus, first liquid crystal molecules of a liquid crystal layer 1 c are pretilted by the first alignment layer AL 1 , and second liquid crystal molecules of the liquid crystal layer 1 c are pretilted by the second alignment layer AL 2 . Also, a pretilt-angle of the first liquid crystal molecules may be the same as a pretilt-angle of the second liquid crystal molecules. When electric fields are applied to the liquid crystal layer 1 c , the second liquid crystal molecules on lower alignment areas 1 _aa 1 , 1 _aa 2 , 1 _aa 3 , and 1 _aa 4 provided on the second alignment layer A 12 and the first liquid crystal molecules on upper alignment areas u_aa 1 , u_aa 2 , u_aa 3 , and u_aa 4 provided on the first alignment layer AL 1 are parallelly aligned in the same direction. Since all of the first and second liquid crystal molecules are pretilted, rates at which the first and second liquid crystal molecules are parallelly aligned may be similar to each other.

In such a comparative example of the curved display device 1000 , when a driving voltage is applied to apply the electric fields, the second liquid crystal molecules on the first lower alignment area 1 _aa 1 and the first liquid crystal molecules on the first upper alignment area u_aa 1 are parallelly aligned in a first liquid crystal alignment direction DR 1 , and the second liquid crystal molecules on the second lower alignment area 1 _aa 2 and the first liquid crystal molecules on the second upper alignment area u_aa 2 are parallelly aligned in a second liquid crystal alignment direction DR 2 . The second liquid crystal molecules on the third lower alignment area 1 _aa 3 and the first liquid crystal molecules on the third upper alignment area u_aa 3 are parallelly aligned in a third liquid crystal alignment direction DR 3 , and the second liquid crystal molecules on the fourth lower alignment area 1 _aa 4 and the first liquid crystal molecules on the fourth upper alignment area u_aa 4 are parallelly aligned in a fourth liquid crystal alignment direction DR 4 .

Referring to FIG. 7D , when viewed in a fifth direction D 5 , the first and second alignment layers AL 1 and AL 2 have overlapping areas ova 1 , ova 2 , ova 3 , ova 4 , ova 5 and ova 6 , which overlap each other. The overlapping areas ova 1 , ova 2 , ova 3 , ova 4 , ova 5 , and ova 6 include a first overlapping area ova 1 , a second overlapping area ova 2 , a third overlapping area ova 3 , a fourth overlapping area ova 4 , a fifth overlapping area ova 5 and a sixth overlapping area ova 6 .

In such a comparative example of the curved display device 1000 , all of the first and second liquid crystal molecules are pretilted at substantially the same pretilt-angle on the second overlapping area ova 2 . Thus, an optical axis direction of the liquid crystal layer 1 c on the second overlapping area ova 2 is substantially parallel to an eighth liquid crystal alignment direction DR 8 that is the sum of the first and second liquid crystal alignment directions DR 1 and DR 2 . Similarly, an optical axis direction of the liquid crystal layer 1 c on the fifth overlapping area ova 5 is substantially parallel to a tenth liquid crystal alignment direction DR 10 that is the sum of the third and fourth liquid crystal alignment directions DR 3 and DR 4 .

Such a comparative example of the curved display device 1000 may also include a lower polarization plate pol 1 and an upper polarization plate pol 2 . Here, a first transmission axis pa 1 of the lower polarization plate pol 1 and a second transmission axis pa 2 of an upper polarization plate pol 2 are perpendicular to each other. In such a comparative example of the curved display device 1000 , when the first transmission axis pa 1 of the lower polarization plate pol 1 is parallel to the second direction D 2 , the second transmission axis pa 2 of the upper polarization plate pol 2 is parallel to the first direction D 1 . The first direction D 1 may be parallel to the eighth liquid crystal alignment direction DR 8 or the tenth liquid crystal alignment direction DR 10 .

Thus, when the driving voltage is applied to apply the electric fields in such a comparative example of the curved display device 1000 , the optical axis direction of the liquid crystal layer 1 c within the second and fifth overlapping areas ova 2 and ova 5 may be parallel to a direction of the first transmission layer pa 1 of the lower polarization plate pol 1 or the second transmission layer pa 2 of the upper polarization plate pol 2 .

When the direction of the first transmission axis pa 1 of the lower polarization plate pol 1 is parallel to the optical axis direction of the liquid crystal layer 1 c within each of the second and sixth overlapping areas ova 2 and ova 6 , light passing through the lower polarization plate pol 1 may be blocked by the second transmission axis pa 2 of the upper polarization plate pol 2 after passing through the second and fifth overlapping area ova 2 and ova 5 .

In such a comparative example of the curved display device 1000 , when the direction of the second transmission axis pa 2 of the upper polarization plate pol 2 is parallel to the optical axis direction of the liquid crystal layer 1 c within each of the second and fifth overlapping areas ova 2 and ova 5 , light passing through the lower polarization plate pol 1 may be blocked without passing through the second and fifth overlapping area ova 2 and ova 5 . Thus, the user may see light passed through the second and fifth overlapping areas ova 2 and ova 5 .

That is, in such a comparative example of the curved display device 1000 , the first liquid crystal molecules on the lower alignment areas 1 _aa 1 , 1 _aa 2 , 1 _aa 3 , 1 _aa 4 of the second alignment layer AL 2 and the first liquid crystal molecules on the upper alignment areas u_aa 1 , u_aa 2 , u_aa 3 , u_aa 4 of the first alignment layer AL 1 are aligned in the same direction. Thus, when the first and second substrates are curved, the user may not see light passed through the second and fifth overlapping areas ova 2 and ova 5 , to thereby cause texture defects as the light is darkly seen within the pixel.

In an exemplary embodiment of the curved display device according to invention (e.g., the exemplary embodiments of the curved display device 10 described above with reference to FIG. 6A to 6F ), the pretilted degrees of the first and second liquid crystal molecules (see reference symbols P 1 - 1 and P 2 - 1 of FIG. 4 A) are different from each other by the first and second alignment layers (see reference symbols AL 1 and AL 2 of FIG. 6B ). Thus, when such an embodiment of the curved display device 10 is curved, the texture defects may not occur such that the display quality of the curved display device 10 is substantially improved.

FIGS. 8A and 8B are views illustrating an exemplary embodiment of a method for forming the first and second pretilt liquid crystals illustrated in FIG. 4A .

Referring to FIG. 8A , a display substrate 100 is completely manufactured, and an opposite substrate 300 is completely manufactured. Then, liquid crystal molecules are provided to one of the display substrate 100 and the opposite substrate 300 to couple the display substrate 100 to the opposite substrate 300 . As a result, a liquid crystal layer LC including the liquid crystal molecules is provided, e.g., formed, between the display substrate 100 and the opposite substrate 300 .

When the display substrate 100 and the opposite substrate 300 are coupled to each other, a first alignment layer AL 1 is exposed to the liquid crystal layer LC on the opposite substrate 300 , and a second alignment layer AL 2 is exposed to the liquid crystal layer LC on the display substrate 100 . In such an embodiment, the first alignment layer AL 1 includes first reactive mesogens RM 10 , and the second alignment layer AL 2 includes second reactive mesogens RM 20 . In such an embodiment, an amount of second reactive mesogens RM 20 may be greater than that of first reactive mesogens RM 10 .

Referring to FIG. 8B , in a state where a potential difference between a pixel electrode PE and common electrode CE occurs to generate electric fields in the liquid crystal layer LC, light LT is irradiated onto the liquid crystal layer LC. As a result, the liquid crystal molecules are aligned by the electric fields. Simultaneously, the liquid crystal molecules in which the first and second reactive mesogens RM 10 and RM 20 are aligned by the irradiated light are cured. A second base layer PAL 2 may include a photoinitiator, and a first base layer PAL 1 may not include the photoinitiator. As a result, the most reactive mesogens may move into the second base layer PAL 2 , but may not substantially move into the first base layer PAL 1 .

The second base layer PAL 2 may be formed by using a second alignment solution containing the photoinitiator, and the first base layer PAL 1 may be formed by using a first alignment solution that does not contain the photoinitiator. The second alignment solution may include a photoinitiator, a second solvent and a second alignment agent. The second alignment solution may further include reactive mesogens.

In one exemplary embodiment, for example, the photoinitiator of the second alignment solution may include at least one of benzyl dimethyl ketal, α-hydroxyketone, methylbenzoylformate, acrylophosphine oxide, titALocene, α-amonoketone, α-aminoacetophenone, oxime ester, benzophenone, phenyletone, α-dichloro, acetophenone, α-choro, thioxALthone, and benzionalkylether.

In one exemplary embodiment, for example, the photoinitiator of the second alignment solution may include a commercialized photoinitiator of the photoinitiator including Irgacure® 651, Irgacure® 127, Irgacure® 754, Irgacure® 819, Irgacure® 784, Irgacure® 907, Irgacure® 369, Irgacure® 379, Irgacure® 2959, Irgacure® OXE01, Irgacure® OXE02, Darocure® TPO, which are manufactured by BASF Co. Ltd.

In one exemplary embodiment, for example, the second solvent of the second alignment solution may include one of γ-butyrolactone, ethylene glycol butyl ether, and N-methylpyrrolidone or a mixing solution of at least two of γ-butyrolactone, ethylene glycol butyl ether, and N-methylpyrrolidone.

In one exemplary embodiment, for example, the second alignment solution may include a monomer, dimer, or oligomer of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane, or polystyrene or a mixture thereof.

In one exemplary embodiment, for example, the first alignment solution may include a first solvent and a first alignment agent. The first solvent may include one of γ-butyrolactone, ethylene glycol butyl ether, and N-methylpyrrolidone or a mixing solution of at least two of γ-butyrolactone, ethylene glycol butyl ether, and N-methylpyrrolidone.

In one exemplary embodiment, for example, the first alignment solution may include a monomer, dimer, or oligomer of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane, or polystyrene or a mixture thereof.

The second solvent and a first solvent of the first alignment solution may be substantially the same as or different from each other. Also, the second alignment agent and the first alignment agent may be substantially the same as or different from each other.

The reactive mesogens that move into the second base layer PAL 2 may be polymerized with each other to form second protrusions BU 2 , and a small amount of reactive mesogens moving into the first base layer PAL 1 may be polymerized with each other to form first protrusions BU 1 . The second protrusions BU 2 may include second small-size protrusions SBU 2 and second large-size protrusions LBU 2 . The first protrusions BU 1 may include first small-size protrusions SBU 1 and first large-size protrusions LBU 1 .

The liquid crystal molecules adjacent to the second alignment layer AL 2 of the liquid crystal molecules may be fixed or pretilted to the second alignment layer AL 2 by the second protrusions BU 2 . As a result, second pretilt liquid crystals P 2 are formed on the second alignment layer AL 2 .

In such an embodiment, where an amount of second reactive mesogens is greater than that of first reactive mesogens, an amount of second pretilt liquid crystals P 2 may be greater than that of first pretilt liquid crystals P 1 . In such an embodiment, since an amount of second reactive mesogens respectively coupled or adjacent to the second pretilt liquid crystals P 2 is greater than that of first reactive mesogens respectively coupled or adjacent to the first pretilt liquid crystals P 1 , a pretilt-angle of the second pretilt liquid crystals P 2 may be greater than that of the first pretilt liquid crystals P 1 .

FIG. 9 is a plan view of a pixel of an alternative exemplary embodiment of a curved display device according to the invention, FIG. 10A is a cross-sectional view taken along line III-III′ of FIG. 9 , and FIG. 10B is a cross-sectional view taken along line IV-IV′ of FIG. 9 . The curved display device 501 shown in FIGS. 9, 10A and 10B is substantially the same as the curve display device 500 shown in FIGS. 2 to 4C except for protrusions FP 1 and FP 2 . The same or like elements shown in FIGS. 9, 10A and 10B have been labeled with the same reference characters as used above to describe the exemplary embodiments of the curved display device 500 shown in FIGS. 2 to 4C , and any repetitive detailed description thereof will hereinafter be omitted or simplified.

Referring to FIGS. 9 and 10A , an exemplary embodiment of a curved display device 501 includes a display substrate 101 , an opposite substrate 301 and a liquid crystal layer LC. In such an embodiment, the opposite substrate 301 includes a first base substrate S 1 , a common electrode CE and a first alignment layer AL 1 - 1 . The display substrate 101 includes a second base substrate S 2 , a pixel electrode PE, a second alignment layer AL 2 - 1 , first protrusions FP 1 and second protrusions FP 2 .

Each of the plurality of first protrusions FP 1 extends in a second direction D 2 on a plane. The plurality of first protrusions FP 1 may include an insulation material that is capable of absorbing light, e.g., a material of a light blocking layer BM shown in FIG. 3B . IN such an embodiment, one of the plurality of first protrusions FP 1 may be disposed between the second base substrate S 2 and first vertical stem part VS 1 of a first sub pixel electrode PE 1 to overlap the first vertical stem part VS 1 on a plane. The other one of the plurality of first protrusions FP 1 may be disposed between the second base substrate S 2 and a second vertical stem part VS 2 of a second sub pixel electrode PE 2 to overlap the second vertical stem part VS 2 on a plane.

In an exemplary embodiment, as shown in FIG. 4A , amounts of first and second reactive mesogens RM 10 and RM 20 are different from each other over a pixel area PA so that the pretilt-angles of the first and second pretilt liquid crystals P 1 and P 2 are different from each other. In an alternative exemplary embodiment, as shown in FIGS. 10A and 10B , the pretilt-angles of the first and second pretilt liquid crystals P 10 and P 20 are set to be different from each other on a portion of the pixel area PA by the plurality of first protrusions FP 1 . In such an embodiment, the plurality of first protrusions FP 1 have structures and functions similar to each other, and a structure and function of one of the first protrusion FP 1 , which overlaps the first vertical stem part VS 1 will hereinafter be described in detail for convenience of description.

In such an embodiment, the first protrusion FP 1 may have a shape that protrudes toward the liquid crystal layer LC in a cross-section. Thus, the uppermost side US and a protruded or tilted surface SS may be defined on the first protrusion FP 1 in the cross-section. The tilted surface SS may be connected to the uppermost side US and tilted toward the second base substrate SS.

Since the first protrusion FP 1 is disposed between the first vertical stem part VS 1 and the second base substrate S 2 , a distance between the first vertical stem part VS 1 and the common electrode CE may be reduced by a thickness of the first protrusion part FP 1 . Thus, due to the reduced distance between the first vertical stem part VS 1 and the common electrode CE by of the first protrusion part FP 1 , an intensity of first electric field generated between the first vertical stem part VS 1 disposed on the first protrusion FP 1 and the common electrode CE may be less than that of a second electric field generated between each of first and second branch parts B 1 and B 2 and the common electrode CE. In such an embodiment, a fringe field of the first electric field may increase by the shape of the tilted surface SS.

Liquid crystals that are pretilted by a flat portion of the first alignment layer AL 1 - 1 may be defined as first pretilt liquid crystals P 10 , and liquid crystals adjacent to a curved portion of the second alignment layer AL 2 - 1 to correspond to a position of the tilted surface SS may be defined as second pretilt liquid crystals P 20 . In such an embodiment, as described above, when the intensity of the first electric field is greater than that of the second electric field, and the intensity of the fringe field of the first electric field is increased to be greater than the second electric field, the second pretilt liquid crystals P 20 may be tilted toward the upper most side US. Thus, a second pretilt-angle a 2 of the second pretilt liquid crystals P 20 may be greater than a first pretilt-angle a 1 of the first pretilt liquid crystals P 10 . In such an embodiment, the first and second pretilt-angles a 1 and a 2 are affected by the intensities and directions of the first and second electric fields because a light irradiation process for fixing the first and second pretilt liquid crystals P 10 and P 20 to the first and second alignment layers AL 1 - 1 and AL 2 - 1 is performed in a state where the first and second electric fields are formed.

Thus, as described with reference to FIGS. 4A to 4C , in such an embodiment, where the second pretilt-angle a 2 is greater than the first pretilt-angle a 1 , the tendency in which the liquid crystal molecules behave by the second pretilt liquid crystals P 20 may be stronger than that in which the liquid crystal molecules behave by the first pretilt liquid crystals P 10 .

Accordingly, in such an embodiment, an amount of second liquid crystal molecules P 2 - 1 that are aligned in parallel to the pretilted direction of the second pretilt liquid crystals P 20 in a second space A 2 in response to the electric fields may be greater than that of first liquid crystal molecules P 1 - 1 that are aligned in parallel to the pretilted direction of the first pretilt liquid crystals P 10 in the first space A 1 . Thus, in such an embodiment, an amount of liquid crystal molecules that are aligned in directions opposite to each other on an area on which miss-alignment between the display substrate 101 and the opposite substrate 301 occurs is reduced, such that an occurrence of a factor that deteriorates display quality of the curved display device 501 may be reduced.

Referring to FIGS. 9 and 10B , each of a plurality of second protrusions FP 2 extends along a second direction D 2 on a plane. The plurality of second protrusions FP 2 may include an insulation material. Also, one of the plurality of second protrusions FP 2 may be disposed on the first sub pixel electrode PE 1 to overlap both edges that are parallel to the second direction D 2 of the first sub pixel electrode PE 1 , and the other one of the plurality of second protrusions FP 2 may be disposed on the second sub pixel electrode PE 2 to overlap both ends that are parallel to the second direction D 2 of the second sub pixel electrode PE 2 . Since the plurality of second protrusions FP 2 have structures and functions substantially the same as each other, a structure and function of one of the second protrusion FP 2 that overlaps one edge of the second branch part B 2 of the first sub pixel electrode PE 1 will hereinafter be described in detail.

In such an embodiment, the second protrusion FP 2 may have a shape that protrudes toward the liquid crystal layer LC in a cross-section. Thus, the uppermost side US 1 and a protruded or tilted surface SS 1 may be defined on the second protrusion FP 2 in the cross-section. The tilted surface SS 1 may be connected to the uppermost side US 1 and tilted toward the second base substrate SS.

Unlike the first protrusion FP 1 , the second protrusion FP 2 is disposed on the second branch part B 2 , such that the intensity of the electric fields generated between the second branch part B 2 disposed on the second protrusion FP 2 and the common electrode CE may be less than that of the electric fields generated therearound. Simultaneously, the intensity of the fringe field of the electric fields generated on the second branch part B 2 disposed on the second protrusion FP 2 may increase by the shape of the tilted surface US 1 .

Liquid crystals adjacent to the flat portion of the first alignment layer AL 1 - 1 may be defined as first pretilt liquid crystals P 11 , and liquid crystals adjacent to a curved portion of the second alignment layer AL 2 - 1 to correspond to a position of the tilted surface SS 1 may be defined as second pretilt liquid crystals P 21 . In this case, as illustrated in FIG. 8B , the second pretilt liquid crystals P 21 may be tilted toward a lower side of the tilted surface SS 1 due to characteristics of the electric fields generated on the second branch part B 2 disposed on the second protrusion FP 2 . Thus, a second pretilt-angle a 2 of the second pretilt liquid crystals P 21 may be greater than a first pretilt-angle a 1 of the first pretilt liquid crystals P 11 .

Thus, as described with reference to FIGS. 4A to 4C , in such an embodiment, the second pretilt-angle a 2 is greater than the first pretilt-angle a 1 , such that the tendency in which the second liquid crystal molecules P 2 - 1 behave by the second pretilt liquid crystals P 21 may be stronger than that in which the first liquid crystal molecules P 1 - 1 behave by the first pretilt liquid crystals P 11 . Thus, an amount of second liquid crystal molecules P 2 - 1 may be greater than that of first liquid crystal molecules P 1 - 1 . As a result, since an amount of liquid crystal molecules that are aligned in directions opposite to each other on an area on which miss-alignment between the display substrate 101 and the opposite substrate 301 occurs is reduced, an occurrence of a factor that deteriorates display quality of the curved display device 501 may be reduced.

Hereinafter, features of exemplary embodiments of the invention will be described in greater detail with reference to examples. However, these examples are merely exemplary, and the invention is not limited thereto.

A second base substrate was prepared, and a second base layer was formed on the second base substrate by using a second alignment solution. A first base substrate was prepared, and a first base layer was formed by using a photoinitiator and first alignment solution. A liquid crystal composite including reactive mesogens was provided between the first base substrate and the second base substrate. Then, light and electric fields were provided to form a first alignment including first large-size protrusions and a second alignment layer including second large-size protrusions. The above-described processes were performed to form a curved display device. Samples #1 and #2 were collected as samples of the second alignment layer of Embodiment 1, which is an example according to the invention, and samples #3 and #4 were collected as samples of the first alignment layer of Embodiment 1.

Comparative Example 1

Comparative Example 1 is the same as Embodiment 1 except that the photoinitiator is not used when the second base layer is formed. A curved display device was formed according to Comparative Example 1. Samples #5 and #6 were collected as samples of the second alignment layer of Comparative Example 1, and samples #7 and #8 were collected as samples of the first alignment layer of Comparative Example 1.

1. Measurement According to Embodiment 1 and Comparison Examples 1

1) AFM Measurement

Atomic force microscopy (“AFM”) images of samples #1, #2, #3, and #4 of Embodiment 1 and samples #5, #6, #7, and #8 of Comparative Example 1 were measured by using AFM STA-500. The measured AFM images were illustrated in FIG. 11 .

2) Measurement of Distribution of Large-Size Protrusions

{circle around (1)} Measurement of Distribution of Large-Size Protrusions Each of which has a Particle Diameter of about 30 nm or More

An area on which second large-size protrusions each of which has a particle diameter of about 30 nm or more on the samples #3 and #4 of Embodiment 1 and the samples #7 and #8 of Comparative Example 1 are distributed was measured on the basis of the measured AFM images. Also, an area on which first large-size protrusions, each of which has a particle diameter of about 30 nm or more, on the samples #1 and #2 of Embodiment 1 and the samples #5 and #6 of Comparative Example 1 are distributed was measured based on the measured AFM images. The measured results were illustrated in FIG. 12 . The area on which the second large-size protrusions each of which has a particle diameter of about 30 nm or more or the first large-size protrusions each of which has a particle diameter of about 30 nm or more are distributed was illustrated by a gray color in FIG. 12 , and an area on which the second large-size protrusions having a particle diameter of about 30 nm or more or the first large-size protrusions having a particle diameter of about 30 nm or more are not distributed was illustrated by a black color in FIG. 12 .

{circle around (2)} Measurement of Distribution of Large-Size Protrusions Each of which has a Particle Diameter of about 50 nm or More

An area on which second large-size protrusions each of which has a particle diameter of about 50 nm or more on the samples #3 of Embodiment 1 and the samples #7 and #8 of Comparative Example 1 are distributed was measured based on the measured AFM images. Also, an area on which first large-size protrusions each of which has a particle diameter of about 50 nm or more on the samples #1 and #2 of Embodiment 1 and the samples #5 and #6 of Comparative Example 1 are distributed was measured based on the measured AFM images. The measured results were illustrated in FIG. 12 . The area on which the second large-size protrusions having a particle diameter of about 50 nm or more or the first large-size protrusions having a particle diameter of about 50 nm or more are distributed was illustrated by a gray color in FIG. 13 , and an area on which the second large-size protrusions each of which has a particle diameter of about 50 nm or more or the first large-size protrusions each of which has a particle diameter of about 30 nm or more are not distributed was illustrated by a black color in FIG. 13 .

2. Result of Measurement According to Embodiment 1 and Comparison Examples 1

1) AFM Analysis of First Large-Size Protrusions and Second Large-Size Protrusions

Referring to FIG. 11 , it was seen that the shape, number, distribution of the second large-size protrusions on the samples #5 and #6 of Comparative Example 1 are similar to those of the first large-size protrusions on the samples #7 and #8 of Comparative Example 1. However, it was seen that the number of second large-size protrusions on the samples #1 and #2 of Embodiment 1 is significantly greater than that of first large-size protrusions on the samples #3 and #4 of Embodiment 1.

2) Analysis of Distribution of First Large-Size Protrusions and Second Large-Size Protrusions

{circle around (1)} Analysis of Distribution of Large-Size Protrusions Each of which has a Particle Diameter of about 30 nm or More

Table 1 below shows a surface area of an area on which the first large-size protrusions each of which has a particle diameter of about 30 nm or more and a surface area of an area on which the second large-size protrusions each of which has a particle diameter of about 30 nm or more on the measured AFM images. The sum of a surface area of the area on which the first large-size protrusions each of which has a particle diameter of about 30 nm or more are distributed and a surface area of the area on which the first large-size protrusions each of which has a particle diameter of about 30 nm or more are not distributed on each of the AFM images is 1.0×10 6 nm 2 . The sum of a surface area of the area on which the second large-size protrusions each of which has a particle diameter of about 30 nm or more are distributed and a surface area of the area on which the second large-size protrusions each of which has a particle diameter of about 30 nm or more are not distributed on each of the AFM images is 1.0×10 6 nm 2 .

Referring to Table 1 and FIG. 12 , in Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions is less than that of the distribution area of the second large-size protrusions. Also, Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions is less than that of the non-distribution area of the first large-size protrusions. Also, it was seen that the surface area of the distribution area of the second large-size protrusions is less than that of the non-distribution area of the second large-size protrusions.

In Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions/the surface area of the distribution area of the second large-size protrusions is approximately 43/100, 32/100, ¾, and 57/100.

In Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions/the surface area of the non-distribution area of the first large-size protrusions is approximately ⅕, 17/100, 35/100, 3/10.

However, it was seen that a case in which the surface area of the distribution area of the first large-size protrusions is less than that of the distribution area of the second large-size protrusions is confirmed. Also, Comparative Example 1, it was seen that the surface area of the distribution area of the first large-size protrusions is greater than that of the non-distribution area of the first large-size protrusions. Also, it was seen that the surface area of the distribution area of the second large-size protrusions is less or greater than that of the non-distribution area of the second large-size protrusions.

{circle around (2)} Analysis of Distribution of Large-Size Protrusions Each of which has a Particle Diameter of about 50 nm or More

Table 2 below shows an area on which the first large-size protrusions each of which has a particle diameter of about 50 nm or more and an area on which the second large-size protrusions each of which has a particle diameter of about 50 nm or more on the measured AFM images. The sum of a surface area of the area on which the first large-size protrusions each of which has a particle diameter of about 50 nm or more are distributed and a surface area of the area on which the first large-size protrusions each of which has a particle diameter of about 50 nm or more are not distributed is 1.0×10 6 nm 2 . The sum of a surface area of the area on which the second large-size protrusions each of which has a particle diameter of about 50 nm or more are distributed and a surface area of the area on which the second large-size protrusions each of which has a particle diameter of about 50 nm or more are not distributed on each of the AFM images is 1.0×10 6 nm 2 .

Referring to Table 2 and FIG. 13 , in Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions is less than that of the distribution area of the second large-size protrusions.

In Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions/the surface area of the distribution area of the second large-size protrusions is approximately 42/100, and 32/100.

In Embodiment 1, it was seen that the surface area of the distribution area of the first large-size protrusions/the surface area of the non-distribution area of the first large-size protrusions is approximately 24/1000.

However, in Comparative Example 1, it was seen that the surface area of the distribution area of the first large-size protrusions is less than that of the distribution area of the second large-size protrusions. Also, it was seen that the surface area of the distribution area of the first large-size protrusions/the surface area of the non-distribution area of the first large-size protrusions is approximately 3/10 and 4/10.

In an exemplary embodiment of the curved display device, even though the miss-alignment occurs when the display substrate and opposite substrate which are coupled or adjacent to each other are curved, the pretilt-angles of the pretilt liquid crystals of each of the alignment layer of the display substrate and the alignment layer of the opposite substrate may be adjusted to reduce the liquid crystal molecules that are aligned in directions opposite each other in response to the electric fields in the area on which the miss-alignment occurs. Therefore, in such an embodiment, the display quality of the curved display device may be effectively prevented from being deteriorated as an amount of liquid crystal molecules that are aligned in the direction opposite to each other increases.

It will be apparent to those skilled in the art that various modifications and variations can be made in the invention. Thus, it is intended that the invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Hence, the real protective scope of the invention shall be determined by the technical scope of the accompanying claims.